Hi,
I had a click through the lesson set you mention... perhaps you need to go back a bit and review material so you understand all the terms used.
That said, I've started writing a theory guide in the newsletter recently, and the third installment deals with scale degrees which would seem to be the bit you need most urgently to understand the chord embellishments. You can check it out
here. It's grade 1 music theory, so maybe try reviewing the 3 parts I've written so far... it will probably help.
I didn't see any weird numbers in the tabs or weird fingerings in the tabs or the video so am unsure what you mean there, but here's a quick rundown of the other things you mention:
A major chord is the root, third and fifth notes of the major scale, so a C major chord is the notes C, E and G. A suspended chord has no third, it has been 'suspended'.... or rather replaced, usually by the 4th note in the scale, so a Csus4 would be the notes C, F and G.
A major 7th chord is the root, third, fifth and seventh notes in the scale, so C,E,G and B.
An 'add9' chord is the normal triad (root, third and fifth), plus the ninth note in the scale (hence the 'add 9'). Now, there are only 8 notes in the scale, so it actually means the second note of the scale in the second octave, so you would have C, E, G and D.
If we're in the key of C and you're asked to play the 5 chord, that means to play the chord rooted on the 5th note of the scale, so you would play G major.
I hope that helps...
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